Piezoelectric film element using (Na,K,Li)NbO3

Abstract

A piezoelectric film element is provided, which is capable of improving piezoelectric properties, having on a substrate at least a lower electrode, a lead-free piezoelectric film, and an upper electrode, wherein at least the lower electrode out of the lower electrode and the upper electrode has a crystal structure of a cubic crystal system, a tetragonal crystal system, an orthorhombic crystal system, a hexagonal crystal system, a monoclinic crystal system, a triclinic crystal system, a trigonal crystal system, or has a composition in which one of these crystals exists or two or more of them coexist, and crystal axes of the crystal structure are preferentially oriented to a specific axis smaller than or equal to two axes of these crystals, and a ratio c/a′ is set in a range of 0.992 or more and 0.999 or less, which is the ratio of a crystal lattice spacing c in a direction of a normal line to the substrate surface, with respect to a crystal lattice spacing a′ whose inclination angle from the substrate surface is in a range of 10° or more and 30° or less.

What is claimed is: 
     
       1. A piezoelectric film element, having on a substrate, at least a lower electrode, a lead-free piezoelectric film, and an upper electrode, wherein at least the lower electrode out of the lower electrode and the upper electrode has a crystal structure of a cubic crystal system, a tetragonal crystal system, an orthorhombic crystal system, a hexagonal crystal system, a monoclinic crystal system, a triclinic crystal system, a trigonal crystal system, or has a composition in which one of these crystals exists or two or more of them coexist, and crystal axes of the crystal structure are preferentially oriented to a specific axis smaller than or equal to two axes of these crystals, and a ratio c/a′ is set in a range of 0.992 or more and 0.999 or less, which is the ratio of a crystal lattice spacing c in a direction of a normal line to the substrate surface, with respect to a crystal lattice spacing a′ whose inclination angle from the substrate surface is in a range of 10° or more and 30° or less. 
     
     
       2. The piezoelectric film element according to  claim 1 , wherein the piezoelectric film is expressed by a general formula (Na x K y Li z )NbO 3 (0≦x≦1, 0≦y≦1, 0≦z ≦0.2, x+y+z=1). 
     
     
       3. The piezoelectric film element according to  claim 1 , wherein the ratio c/a′ of the lattice spacing is in a range of 0.993 or more and 0.998 or less. 
     
     
       4. The piezoelectric film element according to  claim 1 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a texture of fine crystal grains each having a columnar structure. 
     
     
       5. The piezoelectric film element according to  claim 1 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a composition of crystal grains with (001) preferential orientation, crystal grains with (110) preferential orientation, and crystal grains with (111) preferential orientation, in which one of these oriented crystals exists or two or more of them coexist. 
     
     
       6. The piezoelectric film element according to  claim 1 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a strain in a state of a tensile stress in a parallel direction to the substrate surface. 
     
     
       7. The piezoelectric film element according to  claim 1   4 ,wherein at least the lower electrode out of the lower electrode and the upper electrode is an electrode layer made of Pt or an alloy mainly composed of Pt, or the electrode layer of a lamination structure including an electrode layer mainly composed of Pt. 
     
     
       8. The piezoelectric film element according to  claim 1 , wherein the substrate is Si substrate. 
     
     
       9. A piezoelectric film device, comprising:
 the piezoelectric film element according to  claim 1 , a function generator or a voltage detection part. 
 
     
     
       10. A piezoelectric film element, having on a substrate at least a lower electrode, a lead-free piezoelectric film, and an upper electrode, wherein at least the lower electrode out of the lower electrode and the upper electrode has a crystal structure of a cubic crystal system, a tetragonal crystal system, an orthorhombic crystal system, a hexagonal crystal system, a monoclinic crystal system, a triclinic crystal system, a trigonal crystal system, or has a composition in which one of these crystals exists or two or more of them coexist, and crystal axes of the crystal structure are preferentially oriented to a specific axis smaller than or equal to two axes of these crystals, and an internal stress σ φ  is set in a range of 0.137 GPa or more and 1.104 GPa or less, which is obtained from the ratio c/a′ of a crystal lattice spacing c in a direction of a normal line to the substrate surface, with respect to a crystal lattice spacing a′ whose inclination angle from the substrate surface is in a range of 10° or more and 30° or less. 
     
     
       11. The piezoelectric film element according to  claim 10 , wherein the piezoelectric film is expressed by a general formula (Na x K y Li z )NbO 3 (0x≦1, 0≦y≦1, 0≦z ≦0.2, x+y+z=1). 
     
     
       12. The piezoelectric film element according to  claim 10 , wherein the internal stress σ 100   is in a range of 0.274 GPa or more and 0.965 or less. 
     
     
       13. The piezoelectric film element according to  claim 10 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a texture of fine crystal grains each having a columnar structure. 
     
     
       14. The piezoelectric film element according to  claim 10 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a composition of crystal grains with (001) preferential orientation, crystal grains with (110) preferential orientation, and crystal grains with (111) preferential orientation, in which one of these oriented crystals exists or two or more of them coexist. 
     
     
       15. The piezoelectric film element according to  claim 10 , wherein at least the lower electrode out of the lower electrode and the upper electrode has a strain in a state of a tensile stress in a parallel direction to the substrate surface. 
     
     
       16. The piezoelectric film element according to  claim 10 , wherein at least the lower electrode out of the lower electrode and the upper electrode is an electrode layer made of Pt or an alloy mainly composed of Pt, or the electrode layer of a lamination structure including an electrode layer mainly composed of Pt. 
     
     
       17. The piezoelectric film element according to  claim 10 , wherein the substrate is Si substrate. 
     
     
       18. A piezoelectric film device, comprising:
 the piezoelectric film element according to  claim 10 , a function generator or a voltage detection part.